Screw-propelled chambered-stern towboat



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I T. a. TARN. SCREW PROPELLED CHAMBERED STERN TOWBOAT.

APPLICATION FILED JULY 22, H9.

Patented July 13, 1920..

f/Z Vania,

NlTD STATES PATENT OFFICE.

SGBEW-PROPELLEZD CHAMBERED-STERN TOVTBQAT.

Specification of Letters Patent.

Patented July 13, 1920.

Application filed July 22, 1919. Serial No. 312,555.

T 0 all whom it may concern:

Be it known that I, Trrorms R. TARN, a citizen of the United States, residing at Brooklyn, in the county of Kings, State of New York, have made a certain new and useful Invention in Screw-Propelled Chambered-Stern Towboats, of which the following is a specification.

This invention relates to screw propelled chambered stern tow boats.

The object of the invention is to provide a screw propelled chambered stern tow boat for operation on rivers or other shallow waters, which' is simple in structure and efficient in operation, and wherein the ability to handle the same is very greatly increased over tow boats of the structure and arrangement heretofore employed.

A. further object is to provide a dual rudder arrangement for twin screw propolled stern chambered tow boats.

A furtherobject is to increase the facility to handle tow boats employed for navigating shallow rivers or other'bodies of water.

Other objects of the invention will appear more fully hereinafter.

The invention consists substantially in the construction, combination, location, and relative arrangement of parts, all as will be more fully hereinafter set forth, as shown in the accompanying drawings, and finally pointed out in the appended claims.

In the drawing:

Figure 1 is a view in section diagram in the vertical longitudinal plan of the axis of a-propeller shaft of a'chambered stern type of vessel. V

Fig. 2 is a similar view in horizontal section.

Fig. 3 is a similar 'view in transverse section.

In the development of freight transpon tation. by water on the shallow and fre quently tortuous inland rivers it has been found that the most economical method of river transportation of freight is accomplished by means of tows arranged in fleets consisting of several units assembled together and propelled by a tow boat usually placed at the rear of the fleet to exert a pushing action thereon. Various types of tow boats for accomplishing this work have been suggested and put into use. Successful operation, however, requires an ability to handle the 'tow boat in negotiating the bends and turns universally encountered in inland waters, particularly of rivers. The great problem, therefore, in this method of freight transportation, lies in the facility with which a tow boat and its tow may be handled, that is, steered in meeting the conditions encountered in navigating shallow and frequently tortuous streams. Involved in this problem of facility of handling is, of course, the type of boat, the character of the propelling power, the structure of the boat itself, the character of the steering apparatus, and the methods of handling the steering and propelling devices. Various types of boats are now employed including the familiar type of stern and side paddle boat, the screw propelled tunnel and the screw propelled chamber boats.

The present invention relates particularly to tow boats of the screw propelled chambered type, and the special object in view is to provide a tow boat structure of this type which will secure a minimum of water disturbance in the chamber or chambers in which are located the screw propeller or propellers, due to the inflow of the water to said chamber or chambers, to increase the effective rudder area particularly in the path of the water coming or delivered from the upper portion of the propeller; to increase the chamber space available for receiving the increased rudder area without increasing the depth of submergence of the rudder; and to facilitate the entrance of the water into the chamber or chambers.

I have found that in a tow boat in which these special objects are attained the ability to handle is very greatly increased over other structures and types of boats of the same capacity and power.

In a screw propelled boat of either the tunnel or the chamber type the propelling screws and steering rudders are located in the tunnel or chamber. The volume of water entering the tunnel or chamber is made up of the sum of two quantities, namely, first, a volume represented by the product of the wetted cross section of the boat and the speed of advance of the boat, and, second, a volume equal to that of the water displaced by the propellers. This total volume of water must enter the tunnel or chamber from the sides of the boat. When the speed of advance of the boat is zero the chamber or tunnel with substantial velocity, and in an agitated condition, the re sult is that the propellers exert a much less 'effective action thereof.

If, on the other hand, the velocity is largely taken out of the water entering the chambers, and if the water is restrained from becoming agita-ted or disturbed in its entrance into the chamber, then a much more effective action of the screw propellers is secured because they act upon a more quiescent body of the water. To secure the more eflioient action, therefore, the structure of the boat should be such as to afford an easy and smooth entrance of the waterfrom the sides of the boat into the screw chamber, and to prevent the formation of eddies or whirls or spinning'motion of the water in the chamber due to its entrance thereinto.

I accomplish these results by the construction shown wherein I provide a boat 4 with one or more chambers in the bottom thereof, two chambers 5, 6, being employed in a twin screw propelled boat. Within each chamber is located a screw propeller 7, and'also two rudders indicated at 8, 9, the rudder 8 being located aft of the propeller but in line with the propeller shaft, while the rudder 9 is located forward of the propeller and slightly to one side ofthe propeller shaft. I

The rudder 9 I prefer to make of two parts, namely, an upper part 10 and a lower part 11, see Fig. 1, carried by the same vertical post or stern indicated at 12, but the two parts are spaced apart from each other, or a one'piece rudder having a slot in the two edges thereof, as indicated at 13, to per mit the rudder to turn into angular relation with reference to the propeller shaft, indicated by the dotted line 1%.

,Each chamber 5, 6, is formed between the adjacent longitudinally rearwardly eXtending'members 15 by the side walls 16 of said .members, and the boat bottom or rake surfaces 17. This rake surface, in each chamber is longitudinally Clll'letl in the direction of the length of the boat as shown in F 1 but is fiat or arstraight plane surface in transverse planes as indicated in Fig. 8.

The water line is indicated by the dotted line 18, Figs. 1 and 3. The corners 19 of the longitudinally extending members 15 are curved or rounded off, as clearly shown in Fig. 3.

The result of this structure is that the entrance of the water to the chambers from the sides of the boat and its ejection from the chambers by the action of the propellers is greatly facilitated and the tendency to create swirls or eddies by passing under or around sharp corners is avoided. Again, by reason of the flat wall surfaces 16, 17, of the chambers, any agitation of the water caused by its inflow into the chambers is quickly arrested, and hence the propeller is enabled to act on a comparatively quiescent body of water and is thereforemore elfec tivein its. action.

Thestructure I have described also enables me to employ a dual rudder9 positioned forward of the propeller and having a portion 10 operating above the propeller shaft and a portion 11 operating below the propeller shaft, thus enabling me to greatly when they are at rest. The dual rudder arrangement, that is, the arrangement of the portion 10 of the rudder above the propeller shaft, permits advantage to be taken of the action of the upper portions ofthe propeller blades upon the water which completely fills the 7 closed water sealed chambers, thereby increasing the steering or flanking effect of the rudder due to the projection of the water by the upper port-ion of the propeller blades against the upper portion of the dual rudder. The location of the propeller shaft longitudinally of the chambers prevents the employment of a single rudder which will enable its upper portion to receive the water projected by the upper portion of the propeller, blades and consequently without the upper portion 10 of thedual rudder arrangement there would be loss of this increased action or reaction of flanking or steering effect. I am also enabled to secure a sufficient area or space of chamber to accommodate the propeller and the rudders without diminishing the capacity of the boat.

It will be seen that the rake surface commencingfforward at the-base line 20, below the water line, gradually curves upwardly to a point above the water line over the propeller and then downwardly to the transom 21 below the water line.

I am enabled, in this structure, to utilize to a remarkable degree the reaction effect of the water projected by the upper part of the propeller, upon the upper section of the dual rudder, thereby substantially increasing the ability to handletheboat. Iam also enabled to locate the propellers and rudders closer to the stern of the boat, thereby increasing the "ill steering leverage exerted by the boat upon tow when the latter is in advance of the oat.

Having now set forth the objects and nature of my invention and a structure embodying the principles thereof, what I claim as new and useful and of my own invention, and desire to secure by Letters Patent, is,-

l. Atowboat ofthe chambered type, having a rudder and a propeller both located in the chamber thereof, the chamber being formed between adj acent'spaced apart longitudinally and rearwardly extending members located at the undersurface oftheboat hull, the proximate corners of said members being rounded and the lower surfaces of said members lying in a plane parallel to the surface level of the water and extending the entire longitudinal length of said chamber.

2. A tow boat having a longitudinally curved surface in the exterior of the bottom of its hull, and longitudinally and rearwardly extending members having slight displacement disposed at the sides of said curved surface to form in conjunction there with a water sealed chamber, said members having their lower surfaces lying in a plane parallel to the surface level of the water and extending the entire longitudinal length of said chamber, the proximate corners of said members being rounded and a propeller and a rudder both located in said water sealed chamber.

3. A tow boat having the under surface of the bottom of its hull formed in a curve extending longitudinally of the boat, said curved surface being transversely flat, and longitudinally and rearwardly extending members having a slight displacement disposed at the sides of said inclined curved bottom surface to form a water sealed'chamher, the opposed vertical sides of said longitudinally extending members being flat, the

side edges of said longitudinally extending members being rounded, a propeller and a rudder both located in said chamber.'

4. A tow boat having a longitudinally curved bottom surface and longitudinally and rearwardly extending members of slight displacement located at the sides of said curved surface to form a water sealed chamber, a propeller located in said chamber, rudders also located in said chamber, one

of said rudders located tothe rear and another located forward of the propeller.

5. A" tow boat having a longitudinally curved bottom surface and longitudinally and rearwardly extending members of slight displacement located at the sides of said curved surface to form a water sealed chamber, a propeller located in said chamber, a rudder also located in said chamber, said rudder located forward of said propeller.

6. A tow boat having a longitudinally curved bottom surface and longitudinally and rearwardly extending members of slight displacement located at the sides of said curved surface to form a water sealed chamher, and a rudder also located in said chamber and located forward of said propeller and having portions thereof respectively disposed above and below the propeller shaft.

7 A tow boat having a longitudinally curved bottom surface and longitudinally and rearwardly extending members of slight displacement located at the sides of said curved surface to form a water sealed chamber, and a rudder also located in said chamber, said rudder having a vertical axis laterally displaced with respect to the propeller shaft and having portions thereof respec tively disposed above and below said shaft.

In testimony whereof I have hereunto set my hand on this 15th day of July, A. D.,

THOMAS H. TARN. 

